It is estimated that at least 1 in 25 people you come into contact with on a daily basis has no conscience at all. No capacity for love, or empathy for another. They hide in plain site completely aware that the majority of us don't know their secret. However, once you become useful to such an individual you slowly but surely will find out the horror.

Psychopaths and sociopaths prey on SYMPATHY! It's your sympathy that they appeal mostly too.This was certainly true of my psychopath.

The most reliable sign. The most universal behavior of unscrupulous people is not directed as one might imagine, at our fearfulness. It is perversely an appeal to our sympathy. (pg 107 Martha Stout, ph.d The Sociopath Next Door)

Anytime my psychopath felt my affection waining or felt as if he might be losing his "narcissistic supply" he would begin his pity party. Telling me how lonely he is. How much he needs me. How much he misses me. How he just can not make it through another day alone. He went so far as to call me incessantly for months talking to me for hours about how he's wanting to commit suicide. I, as any feeling person would, would then invite him over and agree to spend time with him poor helpless soul. He repaid me by lying, cheating and messing with my head some more.

Beware of those sympathy seekers. The seekers rarely are the givers of such generosity.

From Psychiatry Times:

Targeting the Vulnerable

Psychopaths are good at spotting exploitable vulnerabilities in others. Many psychopathic scam artists seek lonely individuals and promise them a lifetime of love and partnership. Others target the grief-stricken or those who have suffered a recent setback or breakup and are therefore less apt to look closely at what appears to be a compassionate helping hand. Alternatively, psychopaths may exploit someone’s need to be needed, finding a motherly or fatherly soul that they can milk for sympathy and cash. They are also inclined to marry people with low self-esteem and convince them that they are somehow to blame for any abuse they suffer in the marriage.

The Sympathy Ploy

Psychopaths usually play on the sympathies of others. When people’s empathic responses are aroused, they are less inclined to scrutinize an individual’s behaviour, or they will attribute bad behaviour to an abusive childhood or other trauma. This provokes the sort of nurturing response that enables the psychopath to manipulate and extract what he wants from others. In extreme cases, sympathy and deception are combined as a deadly lure. Serial killer Ted Bundy wore a cast and used crutches to make himself appear harmless and vulnerable to his victims.